Resist composition and method for producing resist pattern

ABSTRACT

A resist composition contains (A) a resin being insoluble or poorly soluble in alkali aqueous solution, but becoming soluble in an alkali aqueous solution by the action of an acid, (B) an acid generator represented by the formula (II), and (D) a compound represented by the formula (I), 
                         
wherein R 1  and R 2 , m and n, R 3  and R 4 , X 1 , R 5  and Z1 +  are defined in the specification.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Application No. 2011-85015filed on Apr. 7, 2011. The entire disclosures of Japanese ApplicationNo. 2011-85015 is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a resist composition and a method forproducing resist pattern.

2. Background Information

A resist composition which contains a resin, an acid generator and aquencher containing 2,6-diisopropylaniline is described in Patentdocument of JP-2006-257078A.

However, a resist pattern formed with the conventional resistcomposition may be not always satisfied with because pattern collapsesand defects occur.

SUMMARY OF THE INVENTION

The present invention provides following inventions of <1> to <4>.

<1> A resist composition containing

(A) a resin being insoluble or poorly soluble in alkali aqueoussolution, but becoming soluble in an alkali aqueous solution by theaction of an acid,

(B) an acid generator represented by the formula (II), and

(D) a compound represented by the formula (I),

wherein R¹ and R² in each occurrence independently represent a C₁ to C₁₂hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or ahalogen atom;

m and n independently represent an integer of 0 to 4;

wherein R³ and R⁴ independently represent a fluorine atom or a C₁ to C₆perfluoroalkyl group;

X¹ represents an C₁ to C₁₇ divalent saturated hydrocarbon group, and oneor more hydrogen atom contained in the divalent saturated hydrocarbongroup may be replaced by a fluorine atom, one or more —CH₂— contained inthe divalent saturated hydrocarbon group may be replaced by —O— or —CO—;

R⁵ represents a group having cyclic ether structure; and

Z1⁺ represents an organic cation.

<2> The resist composition according to <1>, wherein R⁵ in the formula(II) is a group represented by the formula (IIA) or the formula (IIE).

wherein s1 represents an integer of 1 to 4,

t1 represents an integer of 0 to 2,

provided that s1+t1 represents an integer of 1 to 4;

s11 represents an integer of 1 to 4,

t11 represents an integer of 0 to 2;

s12 represents an integer of 1 to 4,

t12 represents an integer of 0 to 2,

provided that s12+t12 represents an integer of 0 to 4;

R⁶ in each occurrence represents a C₁ to C₁₂ saturated hydrocarbongroup, a C₆ to C₁₈ aromatic hydrocarbon group, or two R⁶ are bondedtogether to form a ring, and one or more hydrogen atoms contained in thesaturated hydrocarbon group, the aromatic hydrocarbon group and the ringmay be replaced by a C₁ to C₆ alkyl group or a nitro group, and one ormore —CH₂— contained in the saturated hydrocarbon group and ring may bereplaced by —O—;

u1 represents an integer of 0 to 8;

R⁷ and R⁸ in each occurrence independently represent a hydroxy group, ahalogen atom, a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, a C₁ toC₆ hydroxy alkyl group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxy groupor a C₂ to C₇ acylamino group, or two of R⁷ and/or R⁸ may be bondedtogether to form a single bond or a ring;

u2 and u3 independently represent an integer of 0 to 16;

* represent a bond to X¹.

<3> The resist composition according to <1> or <2>, which furthercomprises a solvent.

<4> A method for producing a resist pattern comprising steps of;

(1) applying the resist composition any one of <1> to <3> onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

According to the resin and the resist composition of the presentinvention, it is possible to achieve satisfactory less pattern collapsesand defects.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

“(Meth)acrylic monomer” means at least one monomer having a structure of“CH₂═CH—CO—” or “CH₂═C(CH₃)—CO—”, as well as “(meth)acrylate” and“(meth)acrylic acid” mean “at least one acrylate or methacrylate” and“at least one acrylic acid or methacrylic acid,” respectively.

The resist composition of the present invention contains;

(A) a resin (hereinafter is sometimes referred to as “resin (A)”), and

(B) an acid generator represented by the formula (II) (hereinafter issometimes referred to as “acid generator (II)”) and

(D) a compound represented by the formula (I) (hereinafter is sometimesreferred to as “compound (I)”).

Further, the present resist composition preferably contains a solvent(hereinafter is sometimes referred to as “solvent (E)”), as needed.

<Resin (A)>

The resin (A) is a resin having properties which is insoluble or poorlysoluble in alkali aqueous solution but becomes soluble in an alkaliaqueous solution by the action of an acid. Here “a resin havingproperties which is insoluble or poorly soluble in alkali aqueoussolution but becomes soluble in an alkali aqueous solution by the actionof an acid” means a resin which has an acid labile group and isinsoluble or poorly soluble in aqueous alkali solution before contactwith the acid, and becomes soluble in aqueous alkali solution aftercontact with an acid.

Therefore, the resin (A) can be produced by polymerizing at least onemonomer having an acid labile group described below (hereinafter issometimes referred to as “acid labile monomer (a1)”).

The resin (A) may also have a structural unit derived from an acidstable monomer and/or a structural unit derived from a known monomer inthis field as long as the resin (A) has the properties described above.

<Acid Labile Monomer (a1)>

The “acid labile group” means a group which has an elimination group andin which the elimination group is detached by contacting with an acidresulting in forming a hydrophilic group such as a hydroxy or carboxygroup. Examples of the acid labile group include a group represented bythe formula (1) and a group represented by the formula (2). Hereinaftera group represented by the formula (1) is sometimes referred to as an“acid labile group (1)”, and a group represented by the formula (2) issometimes referred to as an “acid labile group (2)”.

wherein R^(a1) to R^(a3) independently represent a C₁ to C₈ alkyl groupor a C₃ to C₂₀ alicyclic hydrocarbon group, or R^(a1) and R^(a2) may bebonded together to form a C₂ to C₂₀ divalent hydrocarbon group, *represents a bond. In particular, the bond here represents a bondingsite (the similar shall apply hereinafter for “bond”).

wherein R^(a1′) and R^(a2′) independently represent a hydrogen atom or aC₁ to C₁₂ hydrocarbon group, R^(a3′) represents a C₁ to C₂₀ hydrocarbongroup, or R^(a2′) and R^(a3′) may be bonded together to form a divalentC₂ to C₂₀ hydrocarbon group, and one or more —CH₂— contained in thehydrocarbon group or the divalent hydrocarbon group may be replaced by—O— or —S—, * represents a bond.

Examples of the alkyl group of R^(a1) to R^(a3) include methyl, ethyl,propyl, butyl, pentyl, hexyl and octyl groups.

Examples of the alicyclic hydrocarbon group of R^(a1) to R^(a3) includemonocyclic groups such as cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclichydrocarbon groups such as decahydronaphtyl, adamantyl, norbornyl (i.e.,bicyclo[2.2.1]heptyl), and methyl norbornyl groups as well as groupsbelow.

The alicyclic hydrocarbon group of R^(a1) to R^(a3) preferably has 3 to16 carbon atoms.

When R^(a1) and R^(a2) is bonded together to form the divalenthydrocarbon group, examples of the group —C(R^(a1))(R^(a2))(R^(a3))include groups below. The divalent hydrocarbon group preferably has 3 to12 carbon atoms.

Specific examples of the acid labile group (1) include, for example,

1,1-dialkylalkoxycarbonyl group (a group in which R^(a1) to R^(a3) arealkyl groups, preferably tert-butoxycarbonyl group, in the formula (1)),

2-alkyladamantane-2-yloxycarbonyl group (a group in which R^(a1), R^(a2)and a carbon atom form adamantyl group, and R^(a3) is alkyl group, inthe formula (1)), and

1-(adamantane-1-yl)-1-alkylalkoxycarbonyl group (a group in which R^(a1)and R^(a2) are alkyl group, and R^(a3) is adamantyl group, in theformula (1)).

The hydrocarbon group of R^(a1′) to R^(a3′) includes any of an alkylgroup, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.

Examples of the alkyl group and the alicyclic hydrocarbon group are thesame examples as described above.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the divalent hydrocarbon group which is formed by bondingwith R^(a2′) and R^(a3′) include groups in which one hydrogen atom inthe hydrocarbon group as described above is removed.

At least one of R^(a1′) and R^(a2′) is preferably a hydrogen atom.

Specific examples of the acid labile group (2) include a group below.

The acid labile monomer (a1) is preferably a monomer having an acidlabile group and a carbon-carbon double bond, and more preferably a(meth)acrylic monomer having the acid labile group. In particular, theacid labile monomer (a1) is preferably a monomer having the acid labilegroup (1) and/or the acid labile group (2), and a carbon-carbon doublebond, and more preferably a (meth)acrylic monomer having the acid labilegroup (1).

Among the (meth)acrylic monomer having an acid labile group, it ispreferably a monomer having a C₅ to C₂₀ alicyclic hydrocarbon group.When a resin which can be obtained by polymerizing monomers having bulkystructure such as the alicyclic hydrocarbon group is used, the resistcomposition having excellent resolution tends to be obtained during theproduction of a resist pattern.

Examples of a structural unit derived from the (meth)acrylic monomerhaving the acid labile group and a carbon-carbon double bond preferablyinclude structural units represented by the formula (a1-1) and theformula (a1-2) below. Hereinafter the structural unit represented by theformula (a1-1) and the structural unit represented by the formula (a1-2)are sometimes referred to as “structural unit (a1-1)” and “structuralunit (a1-2)”), respectively, and monomers inducing the structural unit(a1-1) and the structural unit (a1-2) are sometimes referred to as“monomer (a1-1)” and “monomer (a1-2)”), respectively. These may be usedas a single monomer or as a combination of two or more monomers.

wherein L^(a1) and L^(a2) independently represent *—O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents abond to the carbonyl group;

R^(a4) and R^(a5) independently represent a hydrogen atom or a methylgroup;

R^(a6) and R^(a7) independently represent a C₁ to C₈ alkyl group or a C₃to C₁₀ alicyclic hydrocarbon group;

m1 represents an integer 0 to 14;

n1 represents an integer 0 to 10; and

n1′ represents an integer 0 to 3.

In the formula (a1-1) and the formula (a1-2), L^(a1) and L^(a2) arepreferably *—O— or *—O— (CH₂)_(k1′)—CO—O— and more preferably *—O—, herek1′ represents an integer of 1 to 4 and more preferably 1.

R^(a4) and R^(a5) are preferably a methyl group.

Examples of the alkyl group of R^(a6) and R^(a7) include methyl, ethyl,propyl, butyl, pentyl, hexyl and octyl groups. Among these, the alkylgroup of R^(a6) and R^(a7) is preferably a C₁ to C₆ alkyl group,

Examples of the alicyclic group of R^(a6) and R^(a7) include monocyclichydrocarbon groups such as cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclichydrocarbon groups such as decahydronaphtyl, adamantyl, norbornyl (i.e.,bicyclo[2.2.1]heptyl), and methyl norbornyl groups as well as groupsbelow. Among these, the alicyclic group of R^(a6) and R^(a7) ispreferably a C₃ to C₈ alicyclic hydrocarbon group, and more preferably aC₃ to C₆ alicyclic hydrocarbon group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1.

Examples of the monomer (a1-1) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a1-1-1) to the formula (a1-1-8), and morepreferably monomers represented by the formula (a1-1-1) to the formula(a1-1-4) below.

Examples of the monomer (a1-2) include 1-ethylcyclopentane-1-yl(meth)acrylate, 1-ethylcyclohexane-1-yl (meth)acrylate,1-ethylcycloheptane-1-yl (meth)acrylate, 1-methylcyclopentane-1-yl(meth)acrylate and 1-isopropylcyclopentane-1-yl (meth)acrylate. Amongthese, the monomers are preferably monomers represented by the formula(a1-2-1) to the formula (a1-2-12), and more preferably monomersrepresented by the formula (a1-2-3), the formula (a1-2-4), the formula(a1-2-9) and the formula (a1-2-10), and still more preferably monomerrepresented by the formula (a1-2-3) and the formula (a1-2-9) below.

When the resin (A) contains the structural unit (a1-1) and/or thestructural unit (a1-2), the total proportion thereof is generally 10 to95 mol %, preferably 15 to 90 mol %, more preferably 20 to 85 mol %,with respect to the total structural units (100 mol %) of the resin (A).

Examples of a monomer having an acid-labile group (2) and acarbon-carbon double bond include a monomer represented by the formula(a1-5). Hereinafter, such monomer is sometimes referred to as “monomer(a1-5)”. When the resin (A) has the structural unit derived from themonomer (a1-5), a resist pattern tends to be obtained with less defects.

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆alkyl group that optionally has a halogen atom;

L¹, L² and L³ independently represent *—O—, *—S— or *—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents abond to the carbonyl group (—CO—);

sa represents an integer of 0 to 4;

sb represents an integer of 0 to 4;

Z¹ represents a single bond or a C₁ to C₆ alkanediyl group, and one ormore —CH₂— contained in the alkanediyl group may be replaced by —O— or—CO—.

In the formula (a1-5), R³¹ is preferably a hydrogen atom, a methyl groupor trifluoromethyl group;

L¹ is preferably —O—;

L² and L³ are independently preferably *—O— or *—S—, and more preferably—O— for one and —S— for another;

sa is preferably 1;

sb is preferably an integer of 0 to 2;

Z¹ is preferably a single bond or —CH₂—CO—O—.

Examples of the compound represented by the formula (a1-5) includecompounds below.

When the resin (A) contains the structural unit derived from the monomerrepresented by the formula (a1-5), the proportion thereof is generally 1to 50 mol %, preferably 3 to 45 mol %, and more preferably 5 to 40 mol%, with respect to the total structural units (100 mol %) constitutingthe resin (A).

<Acid Stable Monomer>

The resin (A) is preferably a copolymer of monomers which does nothaving the acid labile group and the monomers (a1). Hereinafter themonomer not having the acid labile group is sometimes referred to as“acid stable monomer”.

As the acid stable monomer, a monomer having a hydroxy group or alactone ring is preferable. When a resin containing the structural unitderived from a monomer having hydroxy group (hereinafter such acidstable monomer is sometimes referred to as “acid stable monomer (a2)”)or a acid stable monomer having a lactone ring (hereinafter such acidstable monomer is sometimes referred to as “acid stable monomer (a3)”)is used, the adhesiveness of resist to a substrate and resolution ofresist pattern tend to be improved.

<Acid Stable Monomer (a2)>

The acid stable monomer (a2), which has the hydroxy group, is preferablyselected depending on the kinds of an exposure light source at producingthe resist pattern.

When KrF excimer laser lithography (248 nm), or high-energy irradiationsuch as electron beam or EUV is used for the resist composition, usingthe acid stable monomer having a phenolic hydroxy group such ashydroxystyrene as the acid stable monomer (a2) is preferable.

When ArF excimer laser lithography (193 nm), i.e., short wavelengthexcimer laser lithography is used, using the acid stable monomer havinga hydroxy adamantyl group represented by the formula (a2-1) as the acidstable monomer (a2) is preferable.

The acid stable monomer (a2) having the hydroxy group may be used as asingle monomer or as a combination of two or more monomers.

Examples of the acid stable monomer having hydroxy adamantyl include themonomer represented by the formula (a2-1).

wherein L^(a3) represents —O— or *—O— (CH₂)_(k2)—CO—O—;

k2 represents an integer of 1 to 7;

* represents a bind to —CO—;

R^(a14) represents a hydrogen atom or a methyl group;

R^(a15) and R^(a16) independently represent a hydrogen atom, a methylgroup or a hydroxy group;

o1 represents an integer of 0 to 10.

In the formula (a2-1), L^(a3) is preferably —O—, —O—(CH₂)_(f1)—CO—O—,here f1 represents an integer of 1 to 4, and more preferably —O—.

R^(a14) is preferably a methyl group.

R^(a15) is preferably a hydrogen atom.

R^(a16) is preferably a hydrogen atom or a hydroxy group.

o1 is preferably an integer of 0 to 3, and more preferably an integer of0 or 1.

Examples of the acid stable monomer represented by the formula (a2-1)include monomers described in JP 2010-204646A. Among these, the monomersare preferably monomers represented by the formula (a2-1-1) to theformula (a2-1-6), more preferably monomers represented by the formula(a2-1-1) to the formula (a2-1-4), and still more preferably monomersrepresented by the formula (a2-1-1) and the formula (a2-1-3) below.

When the resin (A) contains the acid stable structural unit derived fromthe monomer represented by the formula (a2-1), the proportion thereof isgenerally 3 to 45 mol %, preferably 5 to 40 mol %, more preferably 5 to35 mol %, and still more preferably 5 to 20 mol %, with respect to thetotal structural units (100 mol %) constituting the resin (A).

<Acid Stable Monomer (a3)>

The lactone ring included in the acid stable monomer (a3) may be amonocyclic compound such as β-propiolactone ring, γ-butyrolactone,δ-valerolactone, or a condensed ring with monocyclic lactone ring andother ring. Among these, γ-butyrolactone, and condensed ring withγ-butyrolactone and other ring are preferable.

Examples of the acid stable monomer (a3) having the lactone ring includemonomers represented by the formula (a3-1), the formula (a3-2) and theformula (a3-3). These monomers may be used as a single monomer or as acombination of two or more monomers.

wherein L^(a4) to L^(a6) independently represent —O— or *—O—(CH₂)_(k3)—CO—O—;

-   -   k3 represents an integer of 1 to 7, * represents a bind to —CO—;

R^(a18) to R^(a20) independently represent a hydrogen atom or a methylgroup;

R^(a21) in each occurrence represents a C₁ to C₄ alkyl group;

p1 represents an integer of 0 to 5;

R^(a22) to R^(a23) in each occurrence independently represent a carboxylgroup, cyano group and a C₁ to C₄ alkyl group;

-   -   q1 and r1 independently represent an integer of 0 to 3.

Examples of the alkyl group of R^(a21) and R^(a23) include methyl,ethyl, propyl, isopropyl, n-butyl, tert-butyl and sec-butyl groups.

In the formulae (a3-1) to (a3-3), L^(a4) to L^(a6) include the samegroup as described in L^(a3) above, and are independently preferably—O—, *—O— (CH₂)_(k3′)—CO—O—, here k3′ represents an integer of 1 to 4(preferably 1), and more preferably —O—;

R^(a18) to R^(a21) are independently preferably a methyl group.

R^(a22) and R^(a23) are independently preferably a carboxyl group, cyanogroup or methyl group;

p1 to r1 are independently preferably an integer of 0 to 2, and morepreferably an integer of 0 or 1.

Examples of the monomer (a3) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a3-1-1) to the formula (a3-1-4), the formula(a3-2-1) to the formula (a3-2-4), the formula (a3-3-1) to the formula(a3-3-4), more preferably monomers represented by the formula (a3-1-1)to the formula (a3-1-2), the formula (a3-2-3) to the formula (a3-2-4),and still more preferably monomers represented by the formula (a3-1-1)and the formula (a3-2-3) below.

When the resin (A) contains the structural units derived from the acidstable monomer (a3) having the lactone ring, the total proportionthereof is preferably 5 to 70 mol %, more preferably 10 to 65 mol %,still more preferably 10 to 60 mol %, with respect to the totalstructural units (100 mol %) constituting the resin (A).

When the resin (A) is the copolymer of the acid labile monomer (a1) andthe acid stable monomer, the proportion of the structural unit derivedfrom the acid labile monomer (a1) is preferably 10 to 80 mol %, and morepreferably 20 to 60 mol %, with respect to the total structural units(100 mol %) constituting the resin (A).

The proportion of the structural unit derived from the monomer having anadamantyl group (in particular, the monomer having the acid labile group(a1-1)) is preferably 15 mol % or more with respect to the structuralunits derived from the acid labile monomer (a1). As the mole ratio ofthe structural unit derived from the monomer having an adamantyl groupincreases within this range, the dry etching resistance of the resultingresist improves.

The resin (A) preferably is a copolymer of the acid labile monomer (a1)and the acid stable monomer. In this copolymer, the acid labile monomer(a1) is preferably at least one of the acid labile monomer (a1-1) havingan adamantyl group and the acid labile monomer (a1-2) having acyclohexyl or cyclopentyl group, and more preferably is the acid labilemonomer (a1-1).

The acid stable monomer is preferably the acid stable monomer (a2)having a hydroxy group and/or the acid stable monomer (a3) having alactone ring. The acid stable monomer (a2) is preferably the monomerhaving the hydroxyadamantyl group (a2-1).

The acid stable monomer (a3) is preferably at least one of the monomerhaving the γ-butyrolactone ring (a3-1) and the monomer having thecondensed ring of the γ-butyrolactone ring and the norbornene ring(a3-2).

The resin (A) can be produced by a known polymerization method, forexample, radical polymerization method, using at least one of the acidlabile monomer (a1) and/or at least one of the acid stable monomer (a2)having a hydroxy group and/or at least one of the acid stable monomer(a3) having a lactone ring and/or at least one of a known compound.

The weight average molecular weight of the resin (A) is preferably 2,500or more (more preferably 3,000 or more, and still more preferably 4,000or more), and 50,000 or less (more preferably 30,000 or less, and stillmore preferably 15,000 or less). The weight average molecular weight isa value determined by gel permeation chromatography using polystyrene asthe standard product. The detailed condition of this analysis isdescribed in Examples.

The resist composition may contain a resin which is produced bycopolymerizing the acid stable monomers and/or the known monomers inthis field and does not contain the monomer (a1), in addition to theresin (A).

The resist composition of the present invention preferably contains 80weight % or more, and 99 weight % or less of the resin, with respect tothe total solid proportion of the resist composition.

In the specification, the term “solid proportion of the resistcomposition” means the entire proportion of all ingredients other thanthe solvent (E). For example, if the proportion of the solvent (E) is 90weight %, the solid proportion of the resist composition is 10 weight %.

The proportion of the resin (A) and the solid proportion of the resistcomposition can be measured with a known analytical method such as, forexample, liquid chromatography and gas chromatography.

<Acid Generator (II)>

The acid generator (II) is represented by the formula (II) below.

wherein R³ and R⁴ independently represent a fluorine atom or a C₁ to C₆perfluoroalkyl group;

X¹ represents an C₁ to C₁₇ divalent saturated hydrocarbon group, and oneor more hydrogen atom contained in the divalent saturated hydrocarbongroup may be replaced by a fluorine atom, one or more —CH₂— contained inthe divalent saturated hydrocarbon group may be replaced by —O— or —CO—;

R⁵ represents a group having cyclic ether structure; and

Z1⁺ represents an organic cation.

Examples of the perfluoroalkyl group of R³ and R⁴ includetrifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl,perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl,perfluoropentyl and perfluorohexyl groups.

Among these, R³ and R⁴ independently are preferably trifluoromethyl orfluorine atom, and more preferably a fluorine atom.

Examples of the a divalent saturated hydrocarbon group of X¹ include anyof;

a chain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl,heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl,undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl,tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl,heptadecane-1,17-diyl groups, methane-1,1-diyl, ethane-1,1-diyl,propan-1,1-diyl and propan-2,2-diyl groups;

a branched chain alkanediyl group such as a group in which a chainalkanediyl group is bonded a side chain of a C₁ to C₄ alkyl group suchas methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl,for example, butan-1,3-diyl, 2-methylpropane-1,3-diyl,2-methylpropane-1,2-diyl, pentane-1,4-diyl, 2-methylbutane-1,4-diylgroups;

a divalent monocyclic-alicyclic saturated hydrocarbon group such as acycloalkanediyl group (e.g., cyclobutan-1,3-diyl, cyclopentan-1,3-diyl,cyclohexane-1,2-diyl, 1-methylhexane-1,2-diyl, cyclohexane-1,4-diyl,cyclooctan-1,2-diyl, cyclooctan-1,5-diyl groups);

a divalent polycyclic-alicyclic saturated hydrocarbon group such asnorbornane-1,4-diyl, norbornane-2,5-diyl, adamantane-1,5-diyl andadamantane-2,6-diyl groups; and

a combination of two or more groups.

Examples of the saturated hydrocarbon group of X¹ in which one or more—CH₂— contained in the saturated hydrocarbon group is replaced by —O— or—CO— include groups represented by the formula (b1-1) to the formula(b1-6) below. In the formula (b1-1) to the formula (b1-6), the group isrepresented so as to correspond with two sides of the formula (II), thatis, the left side of the group bonds to C(R³)(R⁴)— and the right side ofthe group bonds to R⁵ (examples of the formula (b1-1) to the formula(b1-6) are the same as above). * represents a bond.

wherein L^(b2) represents a single bond or a C₁ to C₁₅ divalentsaturated hydrocarbon group;

L^(b3) represents a single bond or a C₁ to C₁₂ divalent saturatedhydrocarbon group;

L^(b4) represents a C₁ to C₁₃ divalent saturated hydrocarbon group, thetotal number of the carbon atoms in L^(b3) and L^(b4) is at most 13;

L^(b5) represents a C₁ to C₁₅ divalent saturated hydrocarbon group;

L^(b6) and L^(b7) independently represent a C₁ to C₁₅ divalent saturatedhydrocarbon group, the total number of the carbon atoms in L^(b6) andL^(b7) is at most 16;

L^(b8) represents a C₁ to C₁₄ divalent saturated hydrocarbon group;

L^(b9) and L^(b10) independently represent a C₁ to C₁₁ divalentsaturated hydrocarbon group, the total number of the carbon atoms inL^(b9) and L^(b10) is at most 12.

Among these, X¹ is preferably the groups represented by the formula(b1-1) to the formula (b1-4), more preferably the group represented bythe formula (b1-1) or the formula (b1-2), and still more preferably thegroup represented by the formula (b1-1). In particular, the divalentgroup represented by the formula (b1-1) in which L^(b2) represents asingle bond or —CH₂— is preferable.

Specific examples of the divalent group represented by the formula(b1-1) include groups below. In the formula below, * represent a bond.

Specific examples of the divalent group represented by the formula(b1-2) include groups below.

Specific examples of the divalent group represented by the formula(b1-3) include groups below.

Specific examples of the divalent group represented by the formula(b1-4) include a group below.

Specific examples of the divalent group represented by the formula(b1-5) include groups below.

Specific examples of the divalent group represented by the formula(b1-6) include groups below.

The group having cyclic ether structure of R⁵ may be either monocyclicether structure or polycyclic ether structure. Also, the group havingcyclic ether structure includes one or more substituents. The ringstructure having an oxygen atom in the monocyclic ether structure orpolycyclic ether structure preferably has two to five carbon atoms.

Examples of the group having cyclic ether structure include a grouprepresented by the formula (IIA) and a group represented by the formula(IIE).

wherein s1 represents an integer of 1 to 4,

t1 represents an integer of 0 to 2,

provided that s1+t1 represents an integer of 1 to 4;

s11 represents an integer of 1 to 4,

t11 represents an integer of 0 to 2;

s12 represents an integer of 1 to 4,

t12 represents an integer of 0 to 2,

provided that s12+t12 represents an integer of 0 to 4;

R⁶ in each occurrence represents a C₁ to C₁₂ saturated hydrocarbongroup, a C₆ to C₁₈ aromatic hydrocarbon group, or two R⁶ are bondedtogether to form a ring, and one or more hydrogen atoms contained in thesaturated hydrocarbon group, the aromatic hydrocarbon group and the ringmay be replaced by a C₁ to C₆ alkyl group or a nitro group, and one ormore —CH₂— contained in the saturated hydrocarbon group and ring may bereplaced by —O—;

u1 represents an integer of 0 to 8;

R⁷ and R⁸ in each occurrence independently represent a hydroxy group, ahalogen atom, a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, a C₁ toC₆ hydroxy alkyl group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxy groupor a C₂ to C₇ acylamino group, or two of R⁷ and/or R⁸ may be bondedtogether to form a single bond or a ring;

u2 and u3 independently represent an integer of 0 to 16;

* represent a bond to X¹.

Examples of the saturated hydrocarbon group of R⁶ include an alkylgroup, a saturated cyclic hydrocarbon groups (including a spiro ringgroup).

Examples of the alkyl group include methyl, ethyl, propyl, butyl,pentyl, hexyl and octyl groups.

Examples of the saturated cyclic hydrocarbon group include monocyclichydrocarbon groups such as cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclichydrocarbon groups such as decahydronaphtyl, adamantyl, norbornyl (i.e.,bicyclo[2.2.1]heptyl), and methyl norbornyl groups as well as groupsbelow.

Among these, a cycloalkyl group such as cyclohexyl group, and adamantylgroup are preferable as the saturated hydrocarbon group.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

When two R⁶ are bonded together to form a ring, the ring may be any of asaturated or an unsaturated ring. Two R⁶ bonded together to form a ringmay bond to different carbon atoms or the same carbon atom,respectively.

Examples of the alkyl group of R⁷ and R⁸ include the same as those ofgroups in R⁶ described above.

Examples of the alkoxyl group include methoxy, ethoxy, n-propoxy,iso-propoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy, andn-hexyloxy groups.

Examples of the hydroxy alkyl group include hydroxymethyl andhydroxyethyl groups.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the acyloxy group include acetyloxy, propionyloxy andbutyryloxy groups.

Examples of the acylamino group include acetylamino, propionylamino andbutyrylamino groups.

When two of R⁷ and/or R⁸ are bonded together to form a single bond or aring, two R⁷, two R⁸ or two of R⁷ and R⁸ may be bonded together. Inparticular, when two of R⁷ and/or R⁸ are bonded together to form asingle bond, two R⁸ preferably are bonded together.

s1 is preferably 1, t1 is preferably 0 or 1, and s1+t1 is preferably 1or 2.

s12+t12 is preferably 1 or 2.

Examples of the group represented by the formula (IIA) include groupsbelow.

Examples of the group represented by the formula (IIE) include groupsbelow.

Specific examples of the group represented by the formula (IIA) includegroups below.

Specific examples of the group represented by the formula (IIE) includegroups below.

As the group having cyclic ether structure of R⁵, a group including a C₂to C₅ cyclic ether structure is preferable. Example thereof includegroups containing an oxirane ring, oxetane ring, 5-membered cyclic etherstructure having four carbon atoms such as tetra hydro furan and6-membered cyclic ether structure having five carbon atoms such astetrahydro pyrane.

Among these, ether ring structures having two or three carbon atoms arepreferable, ether ring structures such as 3-membered ether ring havingtwo carbon atoms (i.e., oxirane ring) and 4-membered cyclic etherstructure having three carbon atoms (i.e., oxetane ring) are morepreferable, ether ring structures of 3-membered cyclic ether structurehaving two carbon atoms (i.e., oxirane ring) is still more preferable.

The acid generator (II) is preferably an acid generator represented bythe formula (II-a) or the formula (II-b), and more preferably an acidgenerator represented by the formula (II-a).

wherein s1, t1, s11, t11, s12, t12, R³, R⁴, R⁶, R⁷, R⁸, Z1⁺, X¹, u1, u2and u3 have the same meaning as described above.

Examples of the acid generator (II) include salts below.

Examples of Z1⁺ include an organic onium cation, for example, organicsulfonium cation, organic iodonium cation, organic ammonium cation,benzothiazolium cation and organic phosphonium cation. Among these,organic sulfonium cation and organic iodonium cation are preferable, andaryl sulfonium cation is more preferable.

Z1⁺ is preferably represented by any of the formula (b2-1) to theformula (b2-4).

wherein R^(b4), R^(b5) and R^(b6) independently represent a C₁ to C₃₀hydrocarbon group, the hydrocarbon group is preferably a C₁ to C₃₀ alkylgroup, a C₃ to C₁₈ alicyclic hydrocarbon group and a C₆ to C₁₈ aromatichydrocarbon group, the alkyl group may be substituted with a hydroxygroup, a C₁ to C₁₂ alkoxy group or a C₆ to C₁₈ aromatic hydrocarbongroup, the alicyclic hydrocarbon group may be substituted with a halogenatom, a C₂ to C₄ acyl group and a glycidyloxy group, the aromatichydrocarbon group may be substituted with a halogen atom, a hydroxygroup, a C₁ to C₁₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon groupor a C₁ to C₁₂ alkoxy group, or R^(b4) and R^(b5) may be bonded togetherwith a sulfur atom bonded thereto to form a sulfur-containing ring;

R^(b7) and R^(b8) in each occurrence independently represent a hydroxygroup, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxyl group;

m2 and n2 independently represent an integer of 0 to 5;

R^(b9) and R^(b10) independently represent a C₁ to C₁₈ alkyl group or aC₃ to C₁₈ alicyclic hydrocarbon group, or R^(b9) and R^(b10) may bebonded together with a sulfur atom bonded thereto to form asulfur-containing 3- to 12-membered (preferably 3- to 7-membered) ring,and one or more —CH₂— contained in the ring may be replaced by —O—, —S—or —CO—;

R^(b11) represents a hydrogen atom, a C₁ to C₁₈ alkyl group, a C₃ to C₁₈alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group;

R^(b12) represents a C₁ to C₁₂ alkyl group, a C₃ to C₁₈ alicyclichydrocarbon group and a C₆ to C₁₈ aromatic hydrocarbon group, thearomatic hydrocarbon group may be substituted with a C₁ to C₁₂ alkylgroup, a C₁ to C₁₂ alkoxy group, a C₃ to C₁₈ alicyclic hydrocarbon groupor a C₁ to C₁₂ alkyl carbonyloxy group;

R^(b11) and R^(b12) may be bonded together with —CH—CO— bonded theretoto form a 3- to 12-membered (preferably a 3- to 7-membered) ring, andone or more —CH₂— contained in the ring may be replaced by —O—, —S— or—CO—;

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) in eachoccurrence independently represent a hydroxy group, a C₁ to C₁₂ alkylgroup or a C₁ to C₁₂ alkoxy group;

L^(b11) represents —S— or —O—;

o2, p2, s2 and t2 independently represent an integer of 0 to 5;

q2 or r2 independently represent an integer of 0 to 4;

u2 represents an integer of 0 or 1.

Examples of the alkyl group preferably include methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl and2-ethylhexyl groups. Among these, the alkyl group of R^(b9) to R^(b12)is preferably a C₁ to C₁₂ alkyl group.

Examples of the alicyclic hydrocarbon group preferably includemonocyclic groups such as cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclichydrocarbon groups such as decahydronaphtyl, adamantyl, norbornyl (i.e.,bicyclo[2.2.1]heptyl), and methyl norbornyl groups as well as groupsbelow.

Among these, the alicyclic group of R^(b9) to R^(b11) is preferably a C₃to C₁₈ alicyclic group, and more preferably a C₄ to C₁₂ alicyclic group,such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclodecyl, 2-alkyladamantane-2-yl, 1-(adamatane-1-yl)-1-alkyl andisobornyl groups.

Examples of the aromatic hydrocarbon group preferably include an arylgroup such as phenyl, naphthyl, anthryl, p-methylphenyl,p-tert-butylphenyl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl,biphenyl, phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenylgroups. Among these, examples thereof of R^(b12) preferably includephenyl, 4-methylphenyl, 4-ethylphenyl, 4-t-butylphenyl,4-cyclohexylphenyl, 4-methoxyphenyl, naphthyl and biphenyl groups.

Examples of the aromatic group substituted with an alkyl group typicallyrepresent an aralkyl group such as benzyl and phenethyl groups.

Examples of the halogen atom include fluorine, chlorine, bromine oriodine atom.

Examples of the alkoxyl group include methoxy, ethoxy, n-propoxy,iso-propoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy, n-hexyloxy,heptyloxy, octyloxy, 2-ethylhexyloxy, nonyloxy, decyloxy, undecyloxy anddodecyloxy groups.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the alkyl carbonyloxy group of the R^(b12) include methylcarbonyloxy, ethyl carbonyloxy, n-propyl carbonyloxy, isopropylcarbonyloxy, n-butyl carbonyloxy, sec-butyl carbonyloxy, tert-butylcarbonyloxy, pentyl carbonyloxy, hexyl carbonyloxy, octylcarbonyloxy and2-ethylhexylcarbonyloxy groups.

The sulfur atom-containing ring which is formed by R^(b4) and R^(b5) maybe any of monocyclic, polycyclic, aromatic, non-aromatic, saturated andunsaturated rings. Also, the sulfur atom-containing ring may have atleast one of sulfur atom and/or at least one of oxygen atom in additionto one sulfur atom. The sulfur atom-containing ring is preferably a ringhaving 3 to 18 carbon atoms, and more preferably a ring having 4 to 13carbon atoms.

Examples of the ring having a sulfur atom and formed by R^(b9) andR^(b10) bonded together include thiolane-1-ium ring(tetrahydrothiophenium ring), thian-1-ium ring and 1,4-oxathian-4-iumring.

Examples of the ring having —CH—CO— and formed by R^(b11) and R^(b12)bonded together include oxocycloheptane ring, oxocyclohexane ring,oxonorbornane ring and oxoadamantane ring.

Specific examples of the sulfonate anion include sulfonate anionsdescribed in JP2010-204646A.

Among the cations represented by the formula (b2-1) to the formula(b2-4), the cation represented by the formula (b2-1-1) is preferable,and triphenyl sulfonium cation (v2=w2=x2=0 in the formula (b2-1-1)),diphenyltolyl sulfonium cation (v2=w2=0, x2=1, and R^(b21) is a methylgroup in the formula (b2-1-1)) and tritolyl sulfonium cation(v2=w2=x2=1, R^(b19), R^(b20) and R^(b21) are a methyl group in theformula (b2-1-1)) are more preferable.

wherein R^(b19), R^(b20) and R^(b21) in each occurrence independentlyrepresent a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₃to C₁₈ alicyclic hydrocarbon group or a C₁ to C₁₂ alkoxy group, or twoof R^(b19), R^(b20) and R^(b21) may be bonded together to form a heteroatom-containing ring;

v2 to x2 independently represent an integer of 0 to 5.

In the formula (b2-1-1), R^(b19) to R^(b21) independently preferablyrepresent a halogen atom (and more preferably fluorine atom), a hydroxygroup, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxy group; and

v2 to x2 independently represent preferably 0 or 1.

Specific examples of the cation of the formula (b2-1-1) include a cationbelow.

Specific examples of the cation of the formula (b2-2) include a cationbelow.

Specific examples of the cation of the formula (b2-3) include a cationbelow.

The acid generator (II) is a compound in combination of the above anionand cation. The above anion and cation may optionally be combined, forexample, examples thereof include salts below.

The acid generator (II) can be produced by methods described as oraccording to below (1) to (3). In the formula below, s1, t1, s11, t11,s12, t12, u1, u2, u3, R³, R⁴, R⁵, R⁶, R⁷, R⁸, L^(b2), L^(b3), L^(b4),Z1⁺ have the same meaning as described above.

(1) An acid generator represented by the formula (IIa) in which X¹ inthe formula (II) is a group represented by the formula (b1-1), i.e.,—CO—O-L^(b2)— can be produced by reacting a salt represented by theformula (II-1) with a compound represented by the formula (II-2) in asolvent.

Preferred examples of the solvent include acetonitrile.

(2) An acid generator represented by the formula (II-a-a) in which X¹ inthe formula (II-a) is a group represented by the formula (b1-1), i.e.,—CO—O-L^(b2)— can be produced by reacting a salt represented by theformula (IIA-1) with a compound represented by the formula (IIA-2) in asolvent.

Preferred examples of the solvent include acetonitrile.

Examples of the compound represented by the formula (IIA-2) includeglycidol, 2-hydroxymethyl oxetane and 3-ethyl-3-oxetane methanol.

The salt represented by the formula (IIA-1) can be obtained by reactinga salt represented by the formula (IIA-3) with a compound represented bythe formula (IIA-4), i.e., carbonyldiimidazole in a solvent. Preferredexamples of the solvent include acetonitrile.

The salt represented by the formula (IIA-3) can be formed by a methoddescribed in JP2008-127367A.

(3) An acid generator represented by the formula (II-a-b) in which X¹ inthe formula (II-a) is a group represented by the formula (b1-2), i.e.,—CO—O-L^(b4)-CO—O-L^(b3)— can be produced by reacting a salt representedby the formula (IIB-1) with a compound represented by the formula(IIB-2) in a solvent. Preferred examples of the solvent includeacetonitrile.

The compound represented by the formula (IIB-1) can be obtained byreacting a salt represented by the formula (IIB-2) with a compoundrepresented by the formula (IIB-3), i.e., carbonyldiimidazole in asolvent. Preferred examples of the solvent include acetonitrile.

Examples of the compound represented by the formula (IIB-2) includeglycidol and 2-hydroxymethyl oxetane.

The salt represented by the formula (IIB-2) can be obtained by reactinga salt represented by the formula (IIB-4) with a compound represented bythe formula (IIB-5) in presence of a catalyst in a solvent. Preferredexamples of the solvent include dimethylformamide. Preferred examples ofthe catalyst include potassium carbonate and potassium iodide.

The salt represented by the formula (IIB-4) can be formed by a methoddescribed in JP2008-127367A.

Examples of the compound represented by the formula (IIB-5) includebromo acetic acid.

The acid generator (II) may be used as a single salt or as a combinationof two or more salts.

<Acid Generator (B)>

The resist composition of the present invention may include one or moreknown salt for the acid generator other than the acid generator (II).That is, the resist composition of the present invention may include oneor more other acid generator than the acid generator (II) (hereinafteris sometimes referred to as “acid generator (B)”).

An acid generator (B) is classified into non-ionic-based or ionic-basedacid generator. The present resist composition may be used either acidgenerators.

Examples of the non-ionic-based acid generator include organichalogenated compounds; sulfonate esters such as 2-nitrobenzyl ester,aromatic sulfonate, oxime sulfonate, N-sulfonyl oxyimide, sulfonyloxyketone and diazo naphthoquinone 4-sulfonate; sulfones such asdisulfone, ketosulfone and sulfone diazomethane.

Examples of the ionic acid generator includes onium salts containingonium cation (such as diazonium salts, phosphonium salts, sulfoniumsalts, iodonium salts).

Examples of anion of onium salts include sulfonate anion, sulfonylimideanion and sulfonylmethyde anion.

For the acid generator (B), compounds which generate an acid byradiation described in JP S63-26653-A, JP S55-164824-A, JP S62-69263-A,JP S63-146038-A, JP S63-163452-A, JP S62-153853-A, JP S63-146029-A, U.S.Pat. No. 3,779,778-B, U.S. Pat. No. 3,849,137-B, DE3,914,407-B andEP-126,712-A can be used.

Also, as the acid generator (B), compounds formed according toconventional methods can be used.

The acid generator (B) is preferably a fluorine-containing acidgenerator represented by the formula (B1) as described below. In theacid generator (B1), electropositive Z⁺ hereinafter is sometimesreferred to as “an organic cation”, and electronegative one in which theorganic cation has been removed from the compound is sometimes referredto as “sulfonate anion”.

wherein Q¹ and Q² independently represent a fluorine atom or a C₁ to C₆perfluoroalkyl group;

L^(b1) represents a single bond or an C₁ to C₁₇ divalent saturatedhydrocarbon group, and one or more —CH₂— contained in the divalentsaturated hydrocarbon group may be replaced by —O— or —CO—;

Y represents an optionally substituted C₁ to C₁₈ alkyl group or anoptionally substituted C₃ to C₁₈ saturated alicyclic hydrocarbon group,and one or more —CH₂— contained in the alkyl group and saturatedalicyclic hydrocarbon group may be replaced by —O—, —CO— or —SO₂—,provided that the saturated alicyclic hydrocarbon group in which one ormore —CH₂— is replaced by —O— has a lactone structure; and

Z⁺ represents an organic cation.

Examples of the perfluoroalkyl group of Q¹ and Q² include the same asthose of groups in R³ and R⁴ of the formula (II) described above.

Q¹ and Q² independently are preferably trifluoromethyl or fluorine atom,and more preferably a fluorine atom.

Examples of the a divalent saturated hydrocarbon group of L^(b1) includeany of a chain alkanediyl group, a branched chain alkanediyl group, amonocyclic-alicyclic hydrocarbon group, a polycyclic-alicyclichydrocarbon group and a combination of two or more groups, and the sameas those of groups in X¹ of the formula (II) described above.

Examples of the saturated hydrocarbon group of L^(b1) in which one ormore —CH₂— contained in the saturated hydrocarbon group is replaced by—O— or —CO— include groups represented by the formula (b1-1) to theformula (b1-6) above.

Examples of the aliphatic hydrocarbon group of Y include methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl,octyl, 2-ethylhexyl, nonyl, decyl, undecyl and dodecyl groups. Thealiphatic hydrocarbon group of Y is preferably a C₁ to C₆ alkyl group.

Examples of the saturated alicyclic hydrocarbon group of Y includegroups represented by the formula (Y1) to the formula (Y11).

Y may have a substituent.

Examples of the substituent of Y include a halogen atom, a hydroxygroup, an oxo group, a C₁ to C₁₂ alkyl group, a hydroxy group-containingC₁ to C₁₂ alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group, a C₁ toC₁₂ alkoxy group, a C₆ to C₁₈ aromatic hydrocarbon group, a C₇ to C₂₁aralkyl group, a C₂ to C₄ acyl group, a glycidyloxy group or a—(CH₂)_(j2)—O—CO—R^(b1) group, wherein R^(b1) represents a C₁ to C₁₆alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group or a C₆ to C₁₈aromatic hydrocarbon group, j2 represents an integer of 0 to 4. Thealkyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group andthe aralkyl group of the substituent may further have a substituent suchas a C₁ to C₆ alkyl group, a halogen atom, a hydroxy group and an oxogroup.

Examples of the halogen atom include fluorine, chlorine, bromine oriodine atom.

Examples of the hydroxy group-containing alkyl group includehydroxymethyl and hydroxyethyl groups.

Examples of the alkoxyl group include methoxy, ethoxy, n-propoxy,iso-propoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy, n-hexyloxy,heptyloxy, octyloxy, 2-ethylhexyloxy, nonyloxy, decyloxy, undecyloxy anddodecyloxy groups.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the aralkyl group include benzyl, phenethyl, phenylpropyl,naphthylmethyl and naphthylethyl groups.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of saturated alicyclic hydrocarbon group of Y in which one ormore —CH₂— contained in the saturated alicyclic hydrocarbon group isreplaced by —O—, —CO— or —SO₂— include groups represented by the formula(Y12) to the formula (Y19), the formula (Y25) and the formula (Y26).

Among these, the saturated alicyclic hydrocarbon group is preferably anyone of groups represented by the formula (Y1) to the formula (Y19), morepreferably any one of groups represented by the formula (Y11), (Y14),(Y15) or (Y19), and still more preferably group represented by theformula (Y11) or (Y14).

Examples of Y include the groups below.

When Y represents an alkyl group and L^(b1) represents a C₁ to C₁₇divalent alicyclic hydrocarbon group, the —CH₂— contained in thedivalent alicyclic hydrocarbon group bonding Y is preferably replaced byan oxygen atom or carbonyl group. In this case, the —CH₂— contained inthe alkyl group constituting Y is not replaced by an oxygen atom orcarbonyl group.

Y is preferably an optionally substituted C₃ to C₁₈ saturated alicyclichydrocarbon group, more preferably an adamantyl group which isoptionally substituted with, for example, an oxo group and a hydroxygroup, and still more preferably an adamantyl group, a hydroxyadamantylgroup and an oxoadamantyl group.

The sulfonate anion in the salt represented by the formula (B1) ispreferably a sulfonate anions represented by the formula (b1-1-1) to theformula (b1-1-9) below. In the formula (b1-1-1) to the formula (b1-1-9),Q¹, Q² and L^(b2) represents the same meaning as defined above. R^(b2)and R^(b3) independently represent a C₁ to C₄ alkyl group (preferablymethyl group).

Specific examples of the sulfonate anion include sulfonate anionsdescribed in JP2010-204646A.

Examples of the cation of the acid generator (B) include an organiconium cation, for example, organic sulfonium cation, organic iodoniumcation, organic ammonium cation, benzothiazolium cation and organicphosphonium cation. Among these, organic sulfonium cation and organiciodonium cation are preferable, and aryl sulfonium cation is morepreferable.

Examples of the cation Z⁺ of the acid generator (B1) preferably includethe same as those of cations in the formula (b2-1) to the formula (b2-4)described above.

Preferred acid generators (B1) are represented by the formula (B1-1) tothe formula (B1-20). Among these, the formulae (B1-1), (B1-2), (B1-6),(B1-11), (B1-12), (B1-13) and (B1-14) which contain triphenyl sulfoniumcation, and the formulae (B1-3) and (B1-7) which contain tritolylsulfonium cation are preferable.

When the salt represented by the formula (B) is used as the acidgenerator, the salt may be used as a single salt or as a combination oftwo or more salts.

In the resist composition of the present invention in which the acidgenerator (II) is contained as the acid generator, the proportion of theacid generator (II) is preferably not less than 1 parts by weight (andmore preferably not less than 3 parts by weight), and not more than 30parts by weight (and more preferably not more than 25 parts by weight),with respect to 100 parts by weight of the resin (A).

In the resist composition of the present invention in which the acidgenerator (II) is contained together with the acid generator (B), thetotal proportion of the acid generator (II) and the acid generator (B)is preferably not less than 1 parts by weight (and more preferably notless than 3 parts by weight), and not more than 40 parts by weight (andmore preferably not more than 35 parts by weight), with respect to 100parts by weight of the resin (A).

In this case, the weight ratio of the acid generator (II)/acid generator(B) may be 5/95 to 95/5, preferably 10/90 to 90/10, and more preferably15/85 to 85/15.

<Compound (I)>

The compound (I) is the compound represented by the formula (I) below.

wherein R¹ and R² in each occurrence independently represent a C₁ to C₁₂hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or ahalogen atom;

m and n independently represent an integer of 0 to 4.

The hydrocarbon group of R¹ and R² includes any of an aliphatichydrocarbon group, an alicyclic hydrocarbon group, an aromatichydrocarbon group and a combination thereof.

Examples of the aliphatic hydrocarbon group include an alkyl group suchas methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl,pentyl, hexyl and nonyl groups.

The alicyclic hydrocarbon group is any one of monocyclic or polycyclichydrocarbon group, and saturated or unsaturated hydrocarbon group.Examples thereof include a cycloalkyl group such as cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, cyclononyl and cyclododecyl groups;adamantyl and norbornyl groups. The alicyclic hydrocarbon group ispreferably saturated hydrocarbon group.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, 1-naphthyl, 2-naphthyl, 2-methylphenyl, 3-methylphenyl,4-methylphenyl, 4-ethylphenyl, 4-propylphenyl, 4-isopropylphenyl,4-butylphenyl, 4-tert-butylphenyl, 4-hexylphenyl, 4-cyclohexylphenyl,anthryl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the combination thereof include an alkyl-cycloalkyl, acycloalkyl-alkyl, aralkyl (e.g., phenylmethyl, 1-phenylethyl,2-phenylethyl, 1-phenyl-1-propyl, 1-phenyl-2-propyl, 2-phenyl-2-propyl,3-phenyl-1-propyl, 4-phenyl-1-butyl, 5-phenyl-1-pentyl and6-phenyl-1-hexyl groups) groups.

Examples of the alkoxyl group include methoxy and ethoxy groups.

Examples of the acyl group include acetyl, propanoyl, benzoyl andcyclohexanecarbonyl groups.

Examples of the acyloxy group include a group in which oxy group (—O—)bonds to an acyl group.

Examples of the alkoxycarbonyl group include a group in which thecarbonyl group (—CO—) bonds to the alkoxy group, such asmethoxycarbonyl, ethoxycarbonyl, n-propoxycarbonyl, isopropoxycarbonyl,n-butoxycarbonyl, sec-butoxycarbonyl, and tert-butoxycarbonyl groups.

Example of the halogen atom is a chlorine atom, a fluorine atom andbromine atom.

In the formula (I), R¹ and R² in each occurrence independentlypreferably represent a C₁ to C₆ hydrocarbon group, a C₁ to C₄ alkoxylgroup, a C₂ to C₅ acyl group, a C₂ to C₅ acyloxy group, a C₂ to C₅alkoxycarbonyl group, a nitro group or a halogen atom.

m and n independently preferably represent an integer of 0 to 3, morepreferably an integer of 0 to 2, and still more preferably 0.

Specific examples of the compound (I) include compounds below.

The compound (I) can be produced by a method described in “TetrahedronVol. 45, No. 19, p6281-6296”. Also, commercially available compounds canbe used as the compound (I).

In the resist composition of the present invention, the proportion ofthe compound (I) is preferably 0.01 to 5 weight %, and more preferably0.01 to 3 weight %, and still more preferably 0.01 to 1 weight % withrespect to total solid proportion of the resist composition.

<Solvent (E)”>

The resist composition of the present invention may include a solvent(E) in the amount of 90 weight % or more, preferably 92 weight % ormore, and more preferably 94 weight % or more, and 99.9 weight % orless, preferably 99 weight % or less in the composition.

The content of the solvent (E) can be measured with a known analyticalmethod such as, for example, liquid chromatography and gaschromatography.

Examples of the solvent (E) include glycol ether esters such asethylcellosolve acetate, methylcellosolve acetate and propylene glycolmonomethyl ether acetate; glycol ethers such as propylene glycolmonomethyl ether; esters such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; ketones such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and cyclic esters such asγ-butyrolactone. These solvents (E) can be used as a single solvent oras a combination of two or more solvents.

<Basic Compound (C)>

The resist composition of the present invention may contain a basiccompound (C). The basic compound (C) is a compound having a property toquench an acid, in particular, generated from the acid generator (B),and called “quencher”.

As the basic compounds (C), nitrogen-containing basic compounds (forexample, amine and basic ammonium salt) are preferable. The amine may bean aliphatic amine or an aromatic amine. The aliphatic amine includesany of a primary amine, secondary amine and tertiary amine. The aromaticamine includes an amine in which an amino group is bonded to an aromaticring such as aniline, and a hetero-aromatic amine such as pyridine.

Preferred basic compounds (C) include compounds presented by the formula(C1) to the formula (C8) as described below. Among these, the basiccompound presented by the formula (C1-1) is more preferable.

wherein R^(c1), R^(c2) and R^(c3) independently represent a hydrogenatom, a C₁ to C₆ alkyl group, C₅ to C₁₀ alicyclic hydrocarbon group or aC₆ to C₁₀ aromatic hydrocarbon group, one or more hydrogen atomcontained in the alkyl group and alicyclic hydrocarbon group may bereplaced by a hydroxy group, an amino group or a C₁ to C₆ alkoxyl group,one or more hydrogen atom contained in the aromatic hydrocarbon groupmay be replaced by a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, aC₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀ aromatichydrocarbon group.

wherein R^(c2) and R^(c3) independently have the same meaning asdescribed above;

R^(c4) in each occurrence represents a C₁ to C₆ alkyl group, a C₁ to C₆alkoxyl group, a C₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀aromatic hydrocarbon group;

m3 represents an integer 0 to 3.

wherein R^(c5), R^(c6), R^(c7) and R^(c8) independently have the samemeaning as described in R^(c1) of the above;

R^(c9) in each occurrence independently represents a C₁ to C₆ alkylgroup, a C₃ to C₆ alicyclic hydrocarbon group or a C₂ to C₆ alkanoylgroup;

-   -   n3 represents an integer of 0 to 8.

wherein R^(c10), R^(c11), R^(c12), R^(c13) and R^(c16) independentlyhave the same meaning as described in R^(c1) of the above;

R^(c14), R^(c15) and R^(c17) in each occurrence independently have thesame meaning as described in R^(c4) of the above;

o3 and p3 represent an integer of 0 to 3;

L^(c1) represents a divalent C₁ to C₆ alkanediyl group, —CO—, —C(═NH)—,—S— or a combination thereof.

wherein R^(c18), R^(c19) and R^(c20) in each occurrence independentlyhave the same meaning as described in R^(c4) of the above;

q3, r3 and s3 represent an integer of 0 to 3;

L^(c2) represents a single bond, a C₁ to C₆ alkanediyl group, —CO—,—C(═NH)—, —S— or a combination thereof.

In the above formulae, examples of the alkyl group, the alicyclic group,the aromatic group, alkoxy group and the alkanediyl group are the sameexamples described above.

Examples of the alkanoyl group include acetyl group, 2-methylacetylgroup, 2,2-dimethylacetyl group, propionyl group, butylyl group,isobutylyl group, pentanoyl group, and 2,2-dimethylpropionyl group.

Specific examples of the amine represented by the formula (C1) include1-naphtylamine and 2-naphtylamine, aniline, diisopropylaniline, 2-, 3-or 4-methylaniline, 4-nitroaniline, N-methylaniline,N,N-dimethylaniline, diphenylamine, hexylamine, heptylamine, octylamine,nonylamine, decylamine, dibutylamine, dipentylamine, dihexylamine,diheptylamine, dioctylamine, dinonylamine, didecylamine, triethylamine,trimethylamine, tripropylamine, tributylamine, tripentylamine,trihexylamine, triheptylamine, trioctylamine, trinonylamine,tridecylamine, methyldibutylamine, methyldipentylamine,methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine,methyldioctylamine, methyldinonylamine, methyldidecylamine,ethyldibutylamine, ethyldipentylamine, ethyldihexylamine,ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine,ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, ethylenediamine, tetramethylene diamine, hexamethylene diamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane and4,4′-diamino-3,3′-diethyldiphenylmethane.

Among these, diisopropylaniline is preferable, particularly2,6-diisopropylaniline is more preferable as the basic compounds (C)contained in the present resist composition.

Specific examples of the compound represented by the formula (C2)include, for example, piperazine.

Specific examples of the compound represented by the formula (C3)include, for example, morpholine.

Specific examples of the compound represented by the formula (C4)include, for example, piperidine, a hindered amine compound havingpiperidine skeleton described in JP H11-52575-A.

Specific examples of the compound represented by the formula (C5)include, for example, 2,2′-methylenebisaniline.

Specific examples of the compound represented by the formula (C6)include, for example, imidazole and 4-methylimidazole.

Specific examples of the compound represented by the formula (C7)include, for example, pyridine and 4-methylpyridine.

Specific examples of the compound represented by the formula (C8)include, for example, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene,1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane,di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide,2,2′-dipyridylamine, 2,2′-dipicolylamine and bipyridine.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethyl ammonium hydroxide,3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butylammonium salicylate and choline.

The proportion of the basic compound (C) is preferably 0.01 to 5 weight%, more preferably 0.01 to 3 weight %, and still more preferably 0.01 to1 weight % with respect to the total solid proportion of the resistcomposition.

<Other Ingredient (Hereinafter is Sometimes Referred to as “OtherIngredient (F)”>

The resist composition can also include small amounts of variousadditives such as sensitizers, dissolution inhibitors, surfactants,stabilizers, and dyes, as needed.

<Preparing the Resist Composition>

The present resist composition can be prepared by mixing the resin (A),the acid generator (II) and the compound (I), and the acid generator(B), the basic compound (C), the solvent (E) and the other ingredient(F) as needed. There is no particular limitation on the order of mixing.The mixing may be performed in an arbitrary order. The temperature ofmixing may be adjusted to an appropriate temperature within the range of10 to 40° C., depending on the kinds of the resin and solubility in thesolvent (E) of the resin. The time of mixing may be adjusted to anappropriate time within the range of 0.5 to 24 hours, depending on themixing temperature. There is no particular limitation to the tool formixing. An agitation mixing may be adopted.

After mixing the above ingredients, the present resist compositions canbe prepared by filtering the mixture through a filter having about 0.003to 0.2 μm pore diameter.

<Method for Producing Resist Pattern>

The method for producing a resist pattern of the present inventionincludes the steps of:

(1) applying the resist composition of the present invention onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

Applying the resist composition onto the substrate can generally becarried out through the use of a resist application device, such as aspin coater known in the field of semiconductor microfabricationtechnique. The thickness of the applied resist composition layer can beadjusted by controlling the variable conditions of the resistapplication device. These conditions can be selected based on apre-experiment carried out beforehand. The substrate can be selectedfrom various substrates intended to be microfabricated. The substratemay be washed, and an organic antireflection film may be formed on thesubstrate by use of a commercially available antireflection composition,before the application of the resist composition.

Drying the applied composition layer, for example, can be carried outusing a heating device such as a hotplate (so-called “prebake”), adecompression device, or a combination thereof. Thus, the solventevaporates from the resist composition and a composition layer with thesolvent removed is formed. The condition of the heating device or thedecompression device can be adjusted depending on the kinds of thesolvent used. The temperature in this case is generally within the rangeof 50 to 200° C. Moreover, the pressure is generally within the range of1 to 1.0×10⁵ Pa.

The composition layer thus obtained is generally exposed using anexposure apparatus or a liquid immersion exposure apparatus. Theexposure is generally carried out through a mask that corresponds to thedesired pattern. Various types of exposure light source can be used,such as irradiation with ultraviolet lasers such as KrF excimer laser(wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm), F₂ excimerlaser (wavelength: 157 nm), or irradiation with far-ultravioletwavelength-converted laser light from a solid-state laser source (YAG orsemiconductor laser or the like), or vacuum ultraviolet harmonic laserlight or the like. Also, the exposure device may be one which irradiateselectron beam or extreme-ultraviolet light (EUV).

After exposure, the composition layer is subjected to a heat treatment(so-called “post-exposure bake”) to promote the deprotection reaction.The heat treatment can be carried out using a heating device such as ahotplate. The heating temperature is generally in the range of 50 to200° C., preferably in the range of 70 to 150° C.

The composition layer is developed after the heat treatment, generallywith an alkaline developing solution and using a developing apparatus.The development here means to bring the composition layer after the heattreatment into contact with an alkaline solution. Thus, the exposedportion of the composition layer is dissolved by the alkaline solutionand removed, and the unexposed portion of the composition layer remainson the substrate, whereby producing a resist pattern. Here, as thealkaline developing solution, various types of aqueous alkalinesolutions used in this field can be used. Examples include aqueoussolutions of tetramethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (common name: choline).

After the development, it is preferable to rinse the substrate and thepattern with ultrapure water and to remove any residual water thereon.

<Application>

The resist composition of the present invention is useful as the resistcomposition for excimer laser lithography such as with ArF, KrF or thelike, and the resist composition for electron beam (EB) exposurelithography and extreme-ultraviolet (EUV) exposure lithography, as wellas liquid immersion exposure lithography.

The resist composition of the present invention can be used insemiconductor microfabrication and in manufacture of liquid crystals,thermal print heads for circuit boards and the like, and furthermore inother photofabrication processes, which can be suitably used in a widerange of applications.

EXAMPLES

The present invention will be described more specifically by way ofexamples, which are not construed to limit the scope of the presentinvention.

All percentages and parts expressing the content or amounts used in theExamples and Comparative Examples are based on weight, unless otherwisespecified.

The weight average molecular weight is a value determined by gelpermeation chromatography.

Apparatus: HLC-8120GPC type (Tosoh Co. Ltd.)

Column: TSK gel Multipore HXL-M×3+guardcolumn (Tosoh Co. Ltd.)

Eluant: tetrahydrofuran

Flow rate: 1.0 mL/min

Detecting device: RI detector

Column temperature: 40° C.

Injection amount: 100 μL

Standard material for calculating molecular weight: standardpolysthylene (Toso Co. ltd.)

Synthesis Example 1: Synthesis of a Salt Represented by the Formula(II-1)

A salt represented by the formula (II-1-a) was synthesized by the methoddescribed in JP2008-127367A.

10.00 parts of the compound represented by the formula (II-1-a), 50.00parts of acetonitrile and 4.44 parts of the compound represented by theformula (II-1-b) (Trade name: carbonyl diimidazole, Tokyo ChemicalIndustry Co., LTD) were charged, and stirred for 30 minutes at 80° C.After that, the obtained reactant was cooled to 23° C., and filtrated,whereby giving 59.48 parts of a solution containing the salt representedby the formula (II-1-c).

59.48 parts of the salt represented by the formula (II-1-c) and 2.57parts of a compound represented by the formula (II-1-d) (Trade name:3-ethyl-oxetane methanol, Tokyo Chemical Industry Co., LTD were charged,stirred for 1 hour at 23° C., and filtrated. The obtained filtrate wasconcentrated, to this concentrate, 100 parts of chloroform and 30 partsof ion-exchanged water were charged, stirred for 30 minutes, andseparated to obtain an organic layer. These washing with wateroperations were repeated for 3 times. The obtained organic layer wasconcentrated to obtain a concentrate, whereby giving 8.73 parts of thesalt represented by the formula (II-1).

MS(ESI(+) Spectrum): M⁺ 263.1

MS(ESI(−) Spectrum): M⁻ 273.0

Synthesis Example 2: Synthesis of a Salt Represented by the Formula(II-2)

A salt represented by the formula (II-2-a) was synthesized by the methoddescribed in JP2008-127367A.

10.00 parts of the compound represented by the formula (II-2-a), 50.00parts of acetonitrile and 4.44 parts of the compound represented by theformula (II-2-b) (Trade name: carbonyl diimidazole, Tokyo ChemicalIndustry Co., LTD) were charged, and stirred for 30 minutes at 80° C.After that, the obtained reactant was cooled to 23° C., and filtrated,whereby giving 59.68 parts of a solution containing the salt representedby the formula (II-2-c).

59.68 parts of the salt represented by the formula (II-2-c) and 1.64parts of a compound represented by the formula (II-2-d) (Trade name:glycidol, Aldrich Corporation) were charged, stirred for 1 hour at 23°C., and filtrated. The obtained filtrate was concentrated, to thisconcentrate, 100 parts of chloroform and 30 parts of ion-exchanged waterwere charged, stirred for 30 minutes, and separated to obtain an organiclayer. These washing with water operations were repeated for 3 times.The obtained organic layer was concentrated to obtain a concentrate,whereby giving 5.80 parts of the salt represented by the formula (II-2).

MS(ESI(+) Spectrum): M⁺ 263.1

MS(ESI(−) Spectrum): M⁻ 231.0

Synthesis Example 3: Synthesis of a Salt Represented by the Formula(II-3)

A salt represented by the formula (II-3-a) was synthesized by the methoddescribed in JP2008-127367A.

10.00 parts of the compound represented by the formula (II-3-a), 50.00parts of acetonitrile and 4.44 parts of the compound represented by theformula (II-3-b) (Trade name: carbonyl diimidazole, Tokyo ChemicalIndustry Co., LTD) were charged, and stirred for 30 minutes at 80° C.After that, the obtained reactant was cooled to 23° C., and filtrated,whereby giving 59.88 parts of a solution containing the salt representedby the formula (II-3-c).

59.88 parts of the salt represented by the formula (II-3-c) and 3.15parts of a compound represented by the formula (II-3-d) (Trade name:5,5-dimethyl-7-oxabicyclo[4.1.0]heptane-2-o1, Aldrich Corporation) werecharged, stirred for 1 hour at 23° C., and filtrated. The obtainedfiltrate was concentrated, to this concentrate, 100 parts of chloroformand 30 parts of ion-exchanged water were charged, stirred for 30minutes, and separated to obtain an organic layer. These washing withwater operations were repeated for 3 times. The obtained organic layerwas concentrated to obtain a concentrate, whereby giving 5.42 parts ofthe salt represented by the formula (II-3).

MS(ESI(+) Spectrum): M⁺ 263.1

MS(ESI(−) Spectrum): M⁻ 299.0

Synthesis Example 4: Synthesis of a Salt Represented by the Formula(II-4)

10.96 parts of a salt represented by the formula (II-4-a), 50.00 partsof acetonitrile and 4.44 parts of the compound represented by theformula (II-4-b) (Trade name: carbonyl diimidazole, Tokyo ChemicalIndustry Co., LTD) were charged, and stirred for 30 minutes at 80° C.After that, the obtained reactant was cooled to 23° C., and filtrated,whereby giving 60.54 parts of a solution containing the salt representedby the formula (II-4-c).

60.54 parts of the salt represented by the formula (II-4-c) and 2.57parts of a compound represented by the formula (II-4-d) (Trade name:3-ethyl-oxetane methanol, Aldrich Corporation) were charged, stirred for1 hour at 23° C., and filtrated. The obtained filtrate was concentrated,to this concentrate, 100 parts of chloroform and 30 parts ofion-exchanged water were charged, stirred for 30 minutes, and separatedto obtain an organic layer. These washing with water operations wererepeated for 3 times. The obtained organic layer was concentrated toobtain a concentrate, whereby giving 8.92 parts of the salt representedby the formula (II-4).

MS(ESI(+) Spectrum): M⁺ 305.1

MS(ESI(−) Spectrum): M⁻ 273.0

Synthetic Example of the Resin

The monomers used the synthesis of the resin are shown below.

These monomers are referred to as “monomer (A)” to “monomer (I)”.

Synthetic Example 5: Synthesis of Resin A1

Monomer (D), monomer (E), monomer (B), monomer (C) and monomer (F) weremixed together with a mole ratio of monomer (D): monomer (E): monomer(B): monomer (C):monomer (F)=30:14:6:20:30, and dioxane was addedthereto in an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 73° C. After that, the reacted mixture was pouredinto a mixture of a large amount of methanol and water(methanol:water=4:1, weight ratio) to precipitate a resin. The obtainedresin was filtrated. Thus obtained resin was dissolved in anotherdioxane to obtain a solution, and the solution was poured into a largeamount of a mixture of methanol and water to precipitate a resin. Theobtained resin was filtrated. These operations were repeated two timesto reprecipitate and purify, resulting in a 65% yield of copolymerhaving a weight average molecular weight of about 8100. This copolymer,which had the structural units of the following formula, was referred toResin A1.

Synthetic Example 6: Synthesis of Resin A2

Monomer (A), monomer (E), monomer (B), monomer (C) and monomer (F) weremixed together with a mole ratio of monomer (A): monomer (E): monomer(B): monomer (C):monomer (F)=30:14:6:20:30, and dioxane was addedthereto in an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 73° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water(methanol:water=4:1, weight ratio) to precipitate a resin. The obtainedresin was filtrated. Thus obtained resin was dissolved in anotherdioxane to obtain a solution, and the solution was poured into a largeamount of a mixture of methanol and water to precipitate a resin. Theobtained resin was filtrated. These operations were repeated three timesto reprecipitate and purify, resulting in a 68% yield of copolymerhaving a weight average molecular weight of about 7800. This copolymer,which had the structural units of the following formula, was referred toResin A2.

Synthetic Example 7: Synthesis of Resin A3

Monomer (A), monomer (B) and monomer (C) were mixed together with a moleratio of monomer (A): monomer (B): monomer (C)=50:25:25, and dioxane wasadded thereto in an amount equal to 1.5 times by weight of the totalamount of monomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1.0 mol % and 3.0 mol % respectively withrespect to the entire amount of monomers, and the resultant mixture washeated for about 8 hours at 80° C. After that, the obtained reactedmixture was poured into a mixture of a large amount of methanol andwater (methanol:water=4:1, weight ratio) to precipitate a resin. Theobtained resin was filtrated. Thus obtained resin was dissolved inanother dioxane to obtain a solution, and the solution was poured into amixture of methanol and water to precipitate a resin. The obtained resinwas filtrated. These operations were repeated three times toreprecipitate and purify, resulting in a 60% yield of copolymer having aweight average molecular weight of about 9200. This copolymer, which hadthe structural units of the following formula, was referred to Resin A3.

Synthetic Example 8: Synthesis of Resin A4

Monomer (A), monomer (E), monomer (B), monomer (F) and monomer (C) weremixed together with a mole ratio of monomer (A): monomer (E): monomer(B): monomer (F):monomer (C)=30:14:6:20:30, and dioxane was addedthereto in an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 75° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times to reprecipitate and purify,resulting in a 78% yield of copolymer having a weight average molecularweight of about 7200. This copolymer, which had the structural units ofthe following formula, was referred to Resin A4.

Synthetic Example 9: Synthesis of Resin A5

Monomer (A), monomer (G), monomer (B), monomer (F) and monomer (C) weremixed together with a mole ratio of monomer (A): monomer (G): monomer(B): monomer (F):monomer (C)=30:14:6:20:30, and dioxane was addedthereto in an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 75° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times to reprecipitate and purify,resulting in a 78% yield of copolymer having a weight average molecularweight of about 7200. This copolymer, which had the structural units ofthe following formula, was referred to Resin A5.

Synthetic Example 10: Synthesis of Resin A6

Monomer (A), monomer (H), monomer (B), monomer (F) and monomer (C) weremixed together with a mole ratio of monomer (A): monomer (H): monomer(B): monomer (F):monomer (C)=30:14:6:20:30, and dioxane was addedthereto in an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 75° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times, resulting in a 85% yield ofcopolymer having a weight average molecular weight of about 8400. Thiscopolymer, which had the structural units of the following formula, wasreferred to Resin A6.

Synthetic Example 11: Synthesis of Resin A7

Monomer (A), monomer (H), monomer (I), monomer (F) and monomer (C) weremixed together with a mole ratio of monomer (A): monomer (H): monomer(I): monomer (F):monomer (C)=30:15:3:27:20, and dioxane was addedthereto in an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 75° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times, resulting in a 81% yield ofcopolymer having a weight average molecular weight of about 7800. Thiscopolymer, which had the structural units of the following formula, wasreferred to Resin A7.

(Preparing Resist Composition)

Resist compositions were prepared by mixing and dissolving each of thecomponents shown in Table 1, and then filtrating through a fluororesinfilter having 0.2 μm pore diameter.

TABLE 1 (Unit: parts) Acid Compound Basic BP/PEB Resin Generator (I)Compound (° C./° C.) Ex. 1 A1 = 10 II-1 = 1.4 D1 = 0.1 — 95/85 Ex. 2 A2= 10 II-1 = 1.4 D1 = 0.1 — 110/105 Ex. 3 A2 = 10 II-1/B1 = D1 = 0.1 —110/105 0.7/0.7 Ex. 4 A2 = 10 II-1/B1 = D1 = 0.1 — 110/105 1.0/0.4 Ex. 5A3 = 10 II-1 = 1.4 D1 = 0.1 — 110/105 Ex. 6 A4 = 10 II-1 = 1.4 D1 = 0.1— 110/105 Ex. 7 A5 = 10 II-1 = 1.4 D1 = 0.1 — 110/105 Ex. 8 A5 = 10 II-2= 1.4 D1 = 0.1 — 110/105 Ex. 9 A5 = 10 II-3 = 1.4 D1 = 0.1 — 110/105 Ex.10 A5 = 10 II-4 = 1.4 D1 = 0.1 — 110/105 Ex. 11 A6 = 10 II-1 = 1.4 D1 =0.1 — 110/105 Ex. 12 A6 = 10 II-4 = 1.4 D1 = 0.1 — 110/105 Ex. 13 A7 =10 II-1 = 1.4 D1 = 0.1 — 110/105 Ex. 14 A7 = 10 II-4 = 1.4 D1 = 0.1 —110/105 Comparative Ex.

A3 = 10 B2 = 1.4 — C1 = 0.1 110/105 <Resin> Resins A1 to A7 prepared bythe Synthetic Examples <Acid Generator> II-1: prepared by the SyntheticExample 1

II-2: prepared by the Synthetic Example 2

II-3: prepared by the Synthetic Example 3

II-4: prepared by the Synthetic Example 4

B1: this was prepared by a method according to the method described inthe Examples of JP2010-152341A

B2: this was prepared by a method according to the method described inthe Examples of JP2007-161707A

<Basic compound: Qencher> C1: 2,6-diisopropylaniline (obtained fromTokyo Chemical Industry Co., LTD) <Compound (I)> D1: obtained from TokyoChemical Industry Co., LTD

<Solvent of Resist Composition>

Propylene glycol monomethyl ether acetate 265 parts Propylene glycolmonomethyl ether 20 parts 2-Heptanone 20 parts γ-butyrolactone 3.5 parts(Producing Resist Pattern)

A composition for an organic antireflective film (“ARC-29”, by NissanChemical Co. Ltd.) was applied onto 12-inch silicon wafers and baked for60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

The above resist compositions were then applied thereon by spin coatingso that the thickness of the resulting film became 85 nm after drying.

The obtained wafers were then pre-baked for 60 sec on a direct hot plateat the temperatures given in the “PB” column in Table 1 to form acomposition layer.

Line and space patterns were then exposed through stepwise changes inexposure quantity using an ArF excimer laser stepper for immersionlithography (“XT:1900Gi” by ASML Ltd.: NA=1.35, ¾ Annular, X-Ydeflection), on the wafers on which the composition layer had thus beenformed. The ultrapure water was used for medium of immersion.

After the exposure, post-exposure baking was carried out by 60 secondsat the temperatures given in the “PEB” column in Table 1.

Then, puddle development was carried out with 2.38 wt %tetramethylammonium hydroxide aqueous solution for 60 seconds to obtaina resist pattern.

Effective sensitivity was represented as the exposure amount at which a50 nm line and space pattern resolved to 1:1 (line pattern: spacepattern) with the each resist film.

(Pattern collapse (PCM) Evaluation)

Using a mask for forming 45 nm of 1:1 line and space pattern, a resistpattern was prepared at a higher exposure amount than the effectivesensitivity, and observed obtained line pattern by the electron scanningmicroscope.

A “O” was given if the pattern was not observed to disappear patternsdue to collapse or delamination when the line width was finer than 38nm, and

a “X” was given if the pattern was observed to disappear patterns due tocollapse or delamination when the line width is 38 nm or more.

Table 2 illustrates there results. The parenthetical number meansminimum line width (nm) of resolved resist pattern without observationof pattern disappearance.

TABLE 2 PCM Ex. 1 ∘(32) Ex. 2 ∘(31) Ex. 3 ∘(33) Ex. 4 ∘(32) Ex. 5 ∘(36)Ex. 6 ∘(31) Ex. 7 ∘(30) Ex. 8 ∘(34) Ex. 9 ∘(31) Ex. 10 ∘(30) Ex. 11∘(30) Ex. 12 ∘(30) Ex. 13 ∘(30) Ex. 14 ∘(30) Comp. Ex. 1 x(43)

According to the resin and the resist composition of the presentinvention, it is possible to achieve satisfactory less pattern collapsesand defects. Therefore, the present resist composition can be used forsemiconductor microfabrication.

What is claimed is:
 1. A resist composition comprising (A) a resin beinginsoluble or poorly soluble in alkali aqueous solution, but becomingsoluble in an alkali aqueous solution by the action of an acid, andhaving a structural unit represent by the formula (a1-1) or the formula(a1-2), (B) an acid generator represented by the formula (II), and (D) acompound represented by the formula (I),

wherein R¹ and R² in each occurrence independently represent a C₁ to C₁₂hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or ahalogen atom; m and n independently represent an integer of 0 to 4;

wherein R³ and R⁴ independently represent a fluorine atom or a C₁ to C₆perfluoroalkyl group; X¹ represents an C₁ to C₁₇ divalent saturatedhydrocarbon group, and one or more hydrogen atom contained in thedivalent saturated hydrocarbon group may be replaced by a fluorine atom,one or more —CH₂— contained in the divalent saturated hydrocarbon groupmay be replaced by —O— or —CO—; R⁵ represents a group having cyclicether structure; Z1⁺ represents an organic cation; and which furthercomprises a solvent,

in each formula, L^(a1) and L^(a2) independently represent *—O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents abond to the carbonyl group; R^(a4) and R^(a5) independently represent ahydrogen atom or a methyl group; R^(a6) and R^(a7) independentlyrepresent a C₁ to C₈ alkyl group or a C₃ to C₁₀ alicyclic hydrocarbongroup; m1 represents an integer 0 to 14; n1 represents an integer 0 to10; and n1′ represents an integer 0 to 3, wherein R⁵ in the formula (II)is a group represented by the formula (IIA) or the formula (IIE),

wherein s1 is 1 or 2 t1 represents an integer of 0 to 2, provided thats1+t1 is 2 to 3; s11 represents an integer of 1 to 4, t11 represents aninteger of 0 to 2; s12 is 1 or 2, t12 represents an integer of 0 to 2,provided that s12+t12 is 2 to 3; R⁶ in each occurrence represents a C₁to C₁₂ saturated hydrocarbon group, a C₆ to C₁₈ aromatic hydrocarbongroup, or two R⁶ are bonded together to form a ring, and one or morehydrogen atoms contained in the saturated hydrocarbon group, thearomatic hydrocarbon group and the ring may be replaced by a C₁ to C₆alkyl group or a nitro group, and one or more —CH₂— contained in thesaturated hydrocarbon group and ring may be replaced by —O—; u1represents an integer of 0 to 8; R⁷ and R⁸ in each occurrenceindependently represent a hydroxy group, a halogen atom, a C₁ to C₆alkyl group, a C₁ to C₆ alkoxyl group, a C₁ to C₆ hydroxy alkyl group, aC₂ to C₇ acyl group, a C₂ to C₇ acyloxy group or a C₂ to C₇ acylaminogroup, or two of R⁷ and/or R⁸ may be bonded together to form a singlebond or a ring; u2 and u3 independently represent an integer of 0 to 16;and * represents a bond to X¹.
 2. A method for producing a resistpattern comprising steps of; (1) applying the resist composition ofclaim 1 onto a substrate; (2) drying the applied composition to form acomposition layer; (3) exposing the composition layer; (4) heating theexposed composition layer, and (5) developing the heated compositionlayer.